1. Field of the Invention
The present invention relates to an automotive steering system, and more particularly to an improved steering shaft attaching construction.
2. Description of the Related Art
In recent years, with a view to allowing the driver to operate the steering wheel in an eased posture, a number of automotive steering systems have been in use in which the position of the steering wheel can freely be changed. In the automotive steering systems of this type, the position of the steering wheel can optionally be changed according to builds of individual drivers, and known is, for example, a “steering wheel position adjusting apparatus” disclosed in JP-A-2000-16306 (hereinafter, referred to as a “related art (1)”)
As illustrated in FIGS. 8A to 9, the related art (1) relates to an automotive steering system constructed as follows: A stationary bracket 101 is attached to a body of a vehicle. A movable bracket 102 having a downwardly faced U shape when viewed from the back is attached to the stationary bracket 101 so as to be interposed between a pair of left and right support side plates 101a, 101a of the stationary bracket 101 in such a manner as to move back and forth in axial directions of a shaft member 110a (corresponding to a steering shaft). Further, a steering column 110 is attached to the movable bracket 102, and the shaft member 110a is rotatably attached to the steering column 110. With this structure, the positions of the shaft member 110a and a steering wheel 115 provided on the shaft member 110a can be adjusted in the axial directions of the shaft member 110a. 
A specific attaching construction of the movable bracket 102 to the stationary bracket 101 is as follows. Vertically elongate holes 104, 104 extending vertically are formed in the pair of left and right support side plates 101a, 101a of the stationary bracket 101. Horizontally elongate holes 103, 103 extending in the axial direction of the shaft member 110a are formed in a pair of left and right movable support side plates 102b, 102b of the movable bracket 102. Passing a fastening shaft 105 through these horizontally elongate holes 103, 103 and the vertically elongate holes 104, 104 can allow the movable bracket 102 to be attached to the stationary bracket 101 in such a manner as to move back and forth in the axial directions of the shaft member 110a. 
According to the related art (1), the horizontally elongate holes 103, 103 formed in the movable bracket 102 can be displaced in the axial directions of the shaft member 110a relative to the fastening shaft 105 provided on the stationary bracket 101. This allows the movable bracket 102 to slide in the axial directions of the shaft member 110a. 
However, the steering system disclosed in the related art (1) is constructed such that the fastening shaft 105 is fitted in the pair of left and right horizontally elongate holes 103, 103. The center of the left horizontally elongate hole 103 needs to match the center of the right horizontally elongate hole 103, and the width of the left horizontally elongate hole 103 needs to mach the width of the right horizontally elongate hole 103. Unless the required matching is attained, looseness and prizing are generated between the respective horizontally elongate holes 103, 103 and the fastening shaft 105. In this situation, it is not possible to obtain a smooth adjustment operating feeling when the position of the steering wheel 115 is adjusted. In order to attain the smooth adjustment of the steering wheel position, the dimensions of the left and right horizontally elongate holes 103, 103 need to be properly managed with respect to the center positions and widths thereof, thus increasing man hours for such management.
Furthermore, the thickness of the movable support side plates 102b, 102b is relatively small in which the horizontally elongate holes 103, 103 are formed. Since the movable support side plates 102b, 102b are thin, the contact area between the horizontally elongate holes 103, 103 and the fastening shaft 105 when fitted therein becomes small. As a result of this, since the surface pressure becomes relatively large, a certain consideration needs to be taken against wear.
In addition, the horizontally elongate holes 103, 103 are formed by press stamping, and therefore bars are generated thereon when the holes are so formed. Consequently, a certain consideration also needs to be taken not to produce a bad operation feeling due to prizing that would be generated when the fastening shaft 105 is caused to slide within the horizontally elongate holes 103, 103 in implementing a required adjustment.
In order to solve the above problems, a technology disclosed in JP-A-2000-16303 entitled a “steering system” (hereinafter, referred to as a “related art (2)”) may be adopted.
As is illustrated in FIGS. 10 and 11 in the unexamined patent publication, according to the related art (2), a column side bracket 173 having a downwardly faced U shape when viewed from the back is slidably fitted in a body side bracket 172 having a downwardly faced U shape when viewed from the back. Elongate holes 173a, 173b are formed in a pair of left and right side plates of the column side bracket 173, so that frame-like resin sheets 191, 192 are fitted in the elongate holes 173a, 173b, and a bolt 181 on the body side bracket 172 is passed through respective elongate holes in the resin sheets 191, 192.
According to the construction of the related art (2), even if a slight positional and/or dimensional error is generated with respect to the left and right elongate holes 173a, 173b, looseness and prizing that would occur between the bolt 181 and the elongate holes 173a, 173b can be absorbed to some extent.
In the related art (2), however, since components such as the resin sheets 191, 192 and bushes 183, 184 are used, the number of components has to be increased. In the event that the related art (2) so constructed is simply adopted to the related art (1), the construction of an automotive steering system resulting therefrom becomes complicated, and the number of components is increased, which results in an increase in costs. Thus, the simple incorporation of the related art (2) in the related art (1) is not totally advantageous.